Non-equilibrium processes prevail in shaping species richness and functional diversity of terrestrial vertebrates in a global hotspot

Abstract

AbstractAimThe effects of equilibrium and nonequilibrium processes are generally investigated using species richness on a single biological group. However, little is known about how these two classes of processes also affect trait diversity, considering multiple taxa within the same geographical template. Here, we evaluated which variables representing equilibrium (topography, climate, and primary productivity) and nonequilibrium (diversification rate and evolutionary time) processes best explain species richness and trait diversity of four clades of vertebrates within the same global hotspot. We also investigated how trait disparity has accumulated over time and whether there are congruent spatial patterns between groups.LocationAtlantic RainforestTime periodContemporary.Major taxa studiedTerrestrial vertebrates.MethodsWe tested whether the spatial pattern of Functional Dispersion (FDis), richness, diversification rate, and evolutionary time of each group are correlated. We used a spatially explicit structural equation model to test how species richness and functional dispersion are influenced by variables representing equilibrium and nonequilibrium mechanisms. Additionally, we explored how trait disparity accumulated over time in the four groups.ResultsWe found that non-equilibrium proxies, evolutionary time and diversification rate, played a primary role in driving species richness and trait diversity, with elevation and climate variables having only an indirect effect species and trait diversity via diversification rate and evolutionary time. We found a congruent pattern of species richness among all groups, except among ectotherms. In contrast, the spatial distribution of evolutionary time was distinct for each group.Main conclusionsDespite nonequilibrium processes were more important for generating large-scale diversity patterns within the same geographical template, the interplay between evolutionary time and dispersal ability have disparately determined the assembly of communities.